This invention relates to an improved apparatus for providing emergency ventilation to animals, such as poultry or livestock, which are confined in houses specifically designed to enclose the animals while they are fed and allowed to grow to marketable size. Some houses are totally enclosed with some access doors on the sides and on the ends. Electric ventilating fans provide fresh air with oxygen and maintain desired temperatures. Most houses have large open windows on at least two sides and are covered with screen wire. Normally these screened areas are covered with window covers or curtains and are opened only when necessary to provide adequate ventilation for the animals. Under usual circumstances, some electric ventilating fans are used to exhaust air thereby supplying the fresh air with oxygen necessary for good health. Other fans maintain temperatures within required ranges. Under other circumstances electric winches open and close the curtains to supply fresh air and maintain the temperature.
Many animals, especially poultry, have very high metabolic rates, causing the animals to generate large quantities of body heat which must be dissipated constantly. In addition, poultry exhale relatively large amounts of carbon dioxide. When large numbers of birds are confined within a single enclosure, carbon dioxide, being heavier than air, very quickly settles in a layer near the floor. Unless the carbon dioxide is constantly removed, the layer can reach a height sufficient to suffocate the poultry within the house by preventing them from receiving enough oxygen. For this reason, a power failure in the electric ventilation fans or electric curtain winders must be promptly detected and alternate ventilation provided.
Several prior patents disclose various types of methods and devices for automatically lowering the curtains from the ventilation openings present in most confinement houses. For example, U.S. Pat. No. 3,915,377 to the present applicant discloses a device which, upon the occurrence of a power failure, activates a circuit containing a battery which heats a nichrome wire. A nylon cord extends from the apparatus which holds the curtains in a raised position and passes closely adjacent the nichrome wire which burns through the cord, releases the curtains and allows them to drop, thus providing emergency ventilation. Of course, this type of system relies on the proper maintenance and functioning of the backup device so that it operates when a power failure occurs.
A similar device is disclosed in U.S. Pat. No. 3,973,173 to Smith. Smith discloses the use of a capacitor which, after a pre-determined delay, drains current to a solenoid, which retracts a plunger and releases a latching cable connected to the ratchet handle of a winch by which the curtains are maintained in a raised position over the ventilation openings. As with the earlier-described patent, the backup system must be properly maintained and functioning in order to open the curtains and provide ventilation.
The Milroy U.S. Pat. No. 4,056,048 discloses a device which opens a plurality of louvered shutters which are normally held closed by means of electric motors when electric power is available. When a power failure occurs, a spring on each set of louvers causes the louvers to move to an open position.
The invention described below solves many of the problems encountered in connection with the above-described devices by providing a system which releases ventilation curtains or doors upon the occurrence of a power failure without the necessity of secondary means which must properly function in the presence of the power failure.